1. Field of the Invention
The present invention relates generally to tires and more particularly to uninflated tires mounted on conventional pneumatic rims.
2. Description of the Prior Art
Numerous attempts have been made to construct a satisfactory non-pneumatic tire, but, in spite of such efforts extending over many decades, there still exists a need for a non-pneumatic tire having the performance characteristics normally associated with pneumatic tires.
Early tires merely provided a coating of rubber on a rigid wood or metal wheel. Subsequent efforts led to resiliant walled tires, not unlike pneumatic tires, wherein the walls had greater rigidity and structural supportive characteristics than that for pneumatic tires. Such tires had the shortcoming that they could not provide the desired weight support function while providing the necessary cushioning for the load being carried thereby.
Other efforts led to the provision of flexible walled tires having a central circumferential cavity filled with resiliant foam or other cellular structure. These tires, likewise, met with dissatisfaction in that the foam or cellular structure frequently tended to break down after a relatively short service life, and in addition, extreme difficulty was encountered with respect to retaining the tires on the rims.
My patent application Ser. No. 911,204, filed May 31, 1978, is directed to a solid cross section tire of resiliant non-cellular material but, again, difficulties have been encountered in retaining such tires on the rim. My application Ser. No. 919,726, filed June 27, 1978, is directed to a flexible wall tire having an interior circumferential cavity extending thereabout with the cross sectional configuration of the walls of such tires being somewhat V-shaped with the apex thereof riding on the ground to provide somewhat of a bridge characteristic in transmitting the force on the tire rim to the tread surface making contact with the ground. A particular shortcoming experienced in testing tires of this construction, revealed that uninflated flexible wall tires of this type tend to build up somewhat of a bulge or wave immediately ahead of the point where the tire makes contact with the ground. This phenomenon, which may be referred to as a "standing wave", is the source of one of the major difficulties experienced in such tests. This may result in the tire crawling, or walking, around the rim at a rate proportional to the speed of rotation and load thereon. The so called standing wave immediately ahead of the ground contact point, or "footprint" of the tire results in the tire attempting to climb such standing wave and encountering rolling resistance. Further, the bulge tends to force the tire away from the rim on which it is mounted and such tendency is compounded when torque is applied to the wheel. When torque is applied to the loaded rim the bulge on the backside of the footprint is exaggerated frequently resulting in a gap opening up between the tire and rim and sometimes results in the tire itself dismounting the rim when lateral forces are applied between such tire and rim, as for instance during a turn of the front wheel or similar maneuver.
Efforts to solve this problem have led to testing various bonding materials for bonding the wall of the tire directly to the rim but with the present state of the art, no such practical bonding materials have been found and even if such material were available, it would suffer the shortcoming that the aforementioned standing wave would still be developed to some degree and the absolute anchoring of the radially inner edges of the tire sidewalls to the rim to positively prevent shifting thereof would result in extreme sheer stresses being applied to such tire as a result of such standing wave, thus rapidly fatiguing and deteriorating the tire itself.
Thus, there still exists a great demand for a non-pneumatic tire which may be easily and conveniently removably mounted on a conventional rim and which will provide the desired weight carrying function and cushioning during operation without building up a role resisting standing wave ahead of the tire footprint and which will avoid accidental dismounting of the tire from the rim during operation thereof.